Feline calicivirus (FCV) is a common pathogen found in cats. This virus is often detected in multiple cat environments such as shelters and catteries. Feline calicivirus (FCV) infection can cause a variety of manifestations and symptoms including fever, upper respiratory signs, acute or chronic oral disease, limping, and occasionally pneumonia. Vaccination with an attenuated live virus against FCV is widely practiced, and affords moderate protection against acute disease caused by many, but not all, strains of calicivirus. Cats in FCV endemic populations may shed FCV in ocular and nasal discharge, saliva, and feces without showing clinical signs of infection. Such carrier cats may serve as a source of infection for others. In the past, feline caliciviral infection was not usually fatal, however, when death occurred it was most often due to pneumonia or severe upper respiratory infection in young kittens.
FCV infection and disease occur in acute and chronic forms (Studdert, M. J. (1978) Arch. Virol., 58:157-191; Reubel et al., (1992) Vet. Clin. No. Am. Small Anim. Pract., 22:1347-1360), wherein the manifesting signs of acute disease depend on the route (e.g., oral, aerosol) and the strain of virus. The disease may differ in severity, with more virulent strains causing fever; depression; dyspnea; pneumonia; and vesicles and ulcers of the tongue, hard palate and nostrils. Lower virulence strains are less likely to affect the lungs, although other signs are similar. Most FCV carriers are asymptomatic, however, a small proportion will develop a distinct disease syndrome known as chronic plasmacytic or lymphocytic stomatitis or chronic ulceroprolifereative stomatitis (Reubel et al. (1992) supra). This chronic oral disease is progressive and difficult to treat and is perhaps the most prevalent clinical manifestation of FCV as known. Although recognized strains of FCV have not been associated with significant acute mortality, the calicivirus genome is known to be highly mutable (Johnson, R. P., (1992) Can. J. Vet. Res., 56:326-330). Thus, more highly virulent strains may arise at any time.